Urban Heat Island introduction

According to the U.S. Environmental Protection Agency, a "heat island" is an urban or suburban area that is hotter than nearby rural areas. "The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. In the evening, the difference can be as high as 22°F (12°C)." The Soil Science Society of America notes that many Urban Heat Islands experience temperatures up to 10 degrees fahrenheit (5.6 degrees Celsius) warmer than the surrounding countryside.

Urban Heat Islands (UHI) can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution, heat-related illness and mortality. According to the U.S. Census Bureau, roughly 80 percent of Americans live in urban areas. Hence, the vast majority of Americans are experiencing the anthroprogenic (human influenced/created) warming of an UHI. The graphic image shown below depicts the cause and effect of an UHI.

https://www.epa.gov/heat-islands                                                https://heatisland.lbl.gov/

The graphic shows that as a city becomes more developed (Suburban, Urban and Downtown), these areas become progressively warmer than the nearby Rural areas. This is due to the fact that Rural areas contain more vegetation (which helps cool the surrounding area), while Suburban, Urban and Downtown areas have had the local vegetation replaced with sidewalks, streets, parking lots and tall buildings. These man made structures are usually made from cement, asphalt, brick, steel and dark roofs. These materials are very good at absorbing and storing heat from the sun, which creates the UHI effect. The greater the concentration of these man made structures, the greater the anthroprogenic UHI warming.

The Landsat images presented within this web site provide visual evidence of the extent and effect that urbanization has on vegetation areas, and the associated Land Surface Temperatures (LST).